Departmental Seminar at CES on 20 July 2023 at 11:00 am titled "Temperature Sensitivity of soil microbes and extracellular enzyme activity" by Athira Mathew from IISc, Bangalore

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Temperature Sensitivity of soil microbes and extracellular enzyme activity
Athira Mathew, IISc, Bangalore
Date & Time: 
20 Jul 2023 - 11:00am
Event Type: 
Departmental Seminar
CES Seminar Hall, 3rd Floor, Biological Sciences Building

The rise in anthropogenic CO2 emissions has led to a rise in global temperatures which consequently affects global nutrient cycling, including in the largest terrestrial carbon pool in soil. Soil organic carbon is metabolized primarily by micro-organisms, and their activity determines if the soil carbon pool remains a sink or source. Soil microbial respiration accounts for ten folds higher CO2 emissions than anthropogenic sources. Hence soil microbes are crucial for maintaining ecosystem functions such as nutrient cycling and decomposition at proper levels. For decomposition, microbes secrete extracellular enzymes (EEs) in the soil matrix. EEs break down macromolecules into microbially assimilable compounds, which can further be used for their metabolism and growth. Since EEs are protein molecules, their activity changes with temperature making substrate decomposition temperature sensitive. The increase in the activity of EEs under warming can translate to a higher turnover of organic molecules to CO2, which in turn can increase the greenhouse effect creating a net positive feedback loop due to climate change. Previous studies have shown that the rise in soil respiration rate in warming conditions could be attributed to the change in community composition and soil EE activity. Through my thesis, I aim to understand the dependence of soil enzyme activity and microbial community on temperature.  Enzyme activity in soil also changes with space and time. The changes in enzyme activity have been attributed in different studies to climatic, edaphic, and microbial factors. For my first objective, I will do a meta-analysis of the published literature on EE activity in unamended soil to understand the global patterns and drivers of EE activity. But the in-situ measurements of enzyme activity have many limitations; one of the major drawbacks is that they do not take the temperature dependence of enzymes into account. Models of enzyme activities show that the enzyme activity increases with temperature till a critical point. The mechanisms driving temperature dependence in soil EE differ in long-term and short-term warming conditions. In short term it is the physical changes in enzyme kinetics, whereas in the long term it is that biological changes in quantity and quality of enzymes that drive the temperature dependent changes. Thus, my second objective is to understand temperature dependence of soil EEs and identify the possible mechanisms underlying it. Researchers have shown that change in temperature results in the alteration of soil microbial community structure. But the microbial community is known to posses’ high degree of functional redundancy. Hence for my third objective I will evaluate if the changes in soil microbial community due to warming could affect its functionality.  These objectives can improve our understanding of warming on soil microbes and their ecosystem functions. It can help develop better climate change mitigation strategies and pave the way for nature-based climate solutions.